Diffusion of 65Zn in the Mg17Al12 intermetallic compound and in the Mg-33.4 wt.% Al eutectic

Abstract

Abstract The coefficient of 65Zn heterodiffusion in the Mg17Al12 intermetallic compound (β-phase) and the eutectic alloy Mg-33.4 wt.% Al was measured in the temperature region 598 – 698 K using serial sectioning and residual activity methods. The diffusion coefficient of 65Zn in the intermetallic can be written as Δ I = 1.5 × 10– 2 m2 s –1 × exp( – 154.3 kJ mol –1/RT). At temperatures T ≥ 648 K, where the mean diffusion path is greater than the mean interlamellar distance in the eutectic, the effective diffusion coefficient Δ eff = 2.7 × 10– 2 m2 s –1 exp(–155.1 kJ mol– 1/ RT) was evaluated. At two lower temperatures, the diffusion coefficients 65Zn in interphase boundaries were estimated: Δ b (623 K) = 1.6 × 10 –12 m2 τ– 1 and Δ b (598 K) = 4.4 × 10– 13 m2 τ–1. The specific (Mg)/β interfacial energy γ = 140 mJ m– 2 was assessed from measurement of the time dependence of interlamellar distance during isothermal anneal.